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1.与webpack类似的工具还有哪些?谈谈你为什么选择使用或放弃webpack? #

1.1 grunt #

1.1.1 优点 #

1.1.3 执行任务 #

npm run build

1.2 gulp #

1.2.1 优点 #

1.2.2 缺点 #

1.2.3 执行任务 #

npm run build

1.3 webpack #

1.3.1 优点 #

1.3.2 缺点 #

1.3.3 执行任务 #

1.4 rollup #

1.4.1 优点 #

1.4.3 执行任务 #

npm run build

1.5 parcel #

1.5.1 优点 #

1.5.2 缺点 #

2 如何调试webpack代码 #

debug.js

const webpack = require("webpack");
const config = require("./webpack.config.js"); //1.读取配置文件
debugger;
const compiler = webpack(config);
function compilerCallback(err, stats) {
  const statsString = stats.toString();
  console.log(statsString);
}
debugger
compiler.run((err, stats) => {
  compilerCallback(err, stats);
});

3. Loader和Plugin的不同? #

4. webpack的构建流程是什么? #

webpackflow2020

4.1 webpack.config.js #

const path = require("path");
const RunPlugin = require("./plugins/RunPlugin");
const DonePlugin = require("./plugins/DonePlugin");
module.exports = {
  context: process.cwd(),
  mode: "development",
  devtool: false,
  entry: "./src/app.js",
  output: {
    path: path.resolve(__dirname, "dist"),
    filename: "main.js",
  },
  module: {
    rules: [
      {
        test: /\.jsx?$/,
        use: {
          loader: "babel-loader",
          options: {
            presets: ["@babel/preset-env"],
          },
        },
        include: path.join(__dirname, "src"),
        exclude: /node_modules/,
      },
    ],
  },
  plugins: [new RunPlugin(),new DonePlugin()],
  devServer: {},
};

4.2 flow.js #

flow.js

let fs = require('fs');
let path = require('path');
const { SyncHook } = require("tapable");

class Compiler {
  constructor(options) {
    this.options = options;
    this.hooks = {
      run: new SyncHook(),
      done: new SyncHook(),
    };
  }
  run() {
    this.hooks.run.call();  
    let modules = [];
    let chunks = [];
    let files = [];
    // 确定入口:根据配置中的entry找出所有的入口文件
    let entry = path.join(this.options.context, this.options.entry);
    //从入口文件出发,调用所有配置的Loader对模块进行编译,
    let entryContent = fs.readFileSync(entry, "utf8");
    let entrySource = babelLoader(entryContent);
    let entryModule = { id: entry, source: entrySource };
    modules.push(entryModule);
    //再找出该模块依赖的模块,再递归本步骤直到所有入口依赖的文件都经过了本步骤的处理
    let title = path.join(this.options.context, "./src/title.js");
    let titleContent = fs.readFileSync(title, "utf8");
    let titleSource = babelLoader(titleContent);
    let titleModule = { id: title, source: titleSource };
    modules.push(titleModule);
    //根据入口和模块之间的依赖关系,组装成一个个包含多个模块的 Chunk
    let chunk = { name: "main", modules };
    chunks.push(chunk);
    //再把每个Chunk转换成一个单独的文件加入到输出列表
    let file = {
      file: this.options.output.filename,
      source: `
(function (modules) {
   function __webpack_require__(moduleId) {
     var module = { exports: {} };
     modules[moduleId].call(
     module.exports,
     module,
     module.exports,
     __webpack_require__
     );
     return module.exports;
   }
   return __webpack_require__("./src/app.js");
 })(
{
 "./src/app.js": function (module, exports, __webpack_require__) {
     var title = __webpack_require__("./src/title.js");
     console.log(title);
 },
 "./src/title.js": function (module) {
     module.exports = "title";
 },
});
`,
    };
    files.push(file);
    //在确定好输出内容后,根据配置确定输出的路径和文件名,把文件内容写入到文件系统
    let outputPath = path.join(
      this.options.output.path,
      this.options.output.filename
    );
    fs.writeFileSync(outputPath, file.source,'utf8');
      this.hooks.done.call();  
  }
}
//1.从配置文件和Shell语句中读取与合并参数,得出最终的参数
let options = require('./webpack.config');
//2.用上一步得到的参数初始化Compiler对象
let compiler = new Compiler(options);
//3.加载所有配置的插件
if (options.plugins && Array.isArray(options.plugins)) {
  for (const plugin of options.plugins) {
   plugin.apply(compiler);
  }
}
//4.执行对象的run方法开始执行编译
compiler.run();
function babelLoader(source) {
  return `var sum = function sum(a, b) {
              return a + b;
            };`;
}

4.3 RunPlugin.js #

plugins\RunPlugin.js

module.exports = class RunPlugin {
  apply(compiler) {
    compiler.hooks.run.tap("RunPlugin", () => {
      console.log("RunPlugin");
    });
  }
}

4.4 DonePlugin.js #

plugins\DonePlugin.js

module.exports = class DonePlugin {
  apply(compiler) {
    compiler.hooks.done.tap("DonePlugin", () => {
      console.log("DonePlugin");
    });
  }
};

5.有哪些常见的Loader和Plugin?他们是解决什么问题的? #

5.1 loader #

loader 解决问题
babel-loader 把 ES6 或React转换成 ES5
css-loader 加载 CSS,支持模块化、压缩、文件导入等特性
eslint-loader 通过 ESLint 检查 JavaScript 代码
file-loader 把文件输出到一个文件夹中,在代码中通过相对 URL 去引用输出的文件
url-loader 和 file-loader 类似,但是能在文件很小的情况下以 base64 的方式把文件内容注入到代码中去
sass-loader 把Sass/SCSS文件编译成CSS
postcss-loader 使用PostCSS处理CSS
css-loader 主要来处理background:(url)还有@import这些语法。让webpack能够正确的对其路径进行模块化处理
style-loader 把 CSS 代码注入到 JavaScript 中,通过 DOM 操作去加载 CSS。

5.2 plugin #

插件 解决问题
case-sensitive-paths-webpack-plugin 如果路径有误则直接报错
terser-webpack-plugin 使用terser来压缩JavaScript
pnp-webpack-plugin Yarn Plug'n'Play插件
html-webpack-plugin 自动生成带有入口文件引用的index.html
webpack-manifest-plugin 生产资产的显示清单文件
optimize-css-assets-webpack-plugin 用于优化或者压缩CSS资源
mini-css-extract-plugin 将CSS提取为独立的文件的插件,对每个包含css的js文件都会创建一个CSS文件,支持按需加载css和sourceMap
ModuleScopePlugin 如果引用了src目录外的文件报警插件
InterpolateHtmlPlugin 和HtmlWebpackPlugin串行使用,允许在index.html中添加变量
ModuleNotFoundPlugin 找不到模块的时候提供一些更详细的上下文信息
DefinePlugin 创建一个在编译时可配置的全局常量,如果你自定义了一个全局变量PRODUCTION,可在此设置其值来区分开发还是生产环境
HotModuleReplacementPlugin 启用模块热替换
WatchMissingNodeModulesPlugin :此插件允许你安装库后自动重新构建打包文件

5.3 配置 #

5.3.1 webpack.config.js #

'use strict';

const webpack = require('webpack');
const paths = require("./paths");
const CaseSensitivePathsPlugin = require("case-sensitive-paths-webpack-plugin");
const TerserPlugin = require("terser-webpack-plugin");
const PnpWebpackPlugin = require("pnp-webpack-plugin");
const HtmlWebpackPlugin = require("html-webpack-plugin");
const ManifestPlugin = require("webpack-manifest-plugin");
const MiniCssExtractPlugin = require("mini-css-extract-plugin");
const OptimizeCSSAssetsPlugin = require("optimize-css-assets-webpack-plugin");
const InlineChunkHtmlPlugin = require("react-dev-utils/InlineChunkHtmlPlugin");
const WatchMissingNodeModulesPlugin = require("react-dev-utils/WatchMissingNodeModulesPlugin");
const ModuleScopePlugin = require("react-dev-utils/ModuleScopePlugin");
const InterpolateHtmlPlugin = require("react-dev-utils/InterpolateHtmlPlugin");
const ModuleNotFoundPlugin = require("react-dev-utils/ModuleNotFoundPlugin");
const getClientEnvironment = require("./env");
const cssRegex = /\.css$/;
const sassRegex = /\.(scss|sass)$/;
module.exports = function (webpackEnv) {
  console.log("webpackEnv", webpackEnv); //webpackEnv development
  //开发环境
  const isEnvDevelopment = webpackEnv === "development";
  //生产环境
  const isEnvProduction = webpackEnv === "production";
  //set GENERATE_SOURCEMAP=false
  const shouldUseSourceMap = process.env.GENERATE_SOURCEMAP !== "false";
  const shouldInlineRuntimeChunk = process.env.INLINE_RUNTIME_CHUNK !== "false";
  console.log("shouldInlineRuntimeChunk", shouldInlineRuntimeChunk);
  // %PUBLIC_URL% in `index.html` and `process.env.PUBLIC_URL` in JavaScript.
  //忽略结束的/  把环境变量中的变量注入到当前应用中来
  const env = getClientEnvironment(paths.publicUrlOrPath.slice(0, -1));
  console.log("env", env);
  const getStyleLoaders = (cssOptions, preProcessor) => {
    const loaders = [
      isEnvDevelopment && require.resolve("style-loader"),
      isEnvProduction && {
        loader: MiniCssExtractPlugin.loader,
      },
      {
        loader: require.resolve("css-loader"),
        options: cssOptions,
      },
      {
        loader: require.resolve("postcss-loader"),
      },
    ].filter(Boolean);
        if (preProcessor) {
          loaders.push(
            {
              loader: require.resolve("resolve-url-loader")
            },
            {
              loader: require.resolve(preProcessor),
              options: {
                sourceMap: true,
              },
            }
          );
        }
    return loaders;
  };
  return {
    mode: isEnvProduction ? "production" : "development",
    devtool: isEnvProduction
      ? shouldUseSourceMap
        ? "source-map"
        : false
      : isEnvDevelopment && "cheap-module-source-map",
    entry: [
      isEnvDevelopment &&
        require.resolve("react-dev-utils/webpackHotDevClient"),
      paths.appIndexJs,
    ].filter(Boolean),
    output: {
      path: isEnvProduction ? paths.appBuild : undefined, //输出的目标路径
      //一个main bundle一个文件,每个异步代码块也对应一个文件 ,在生产环境中,并不产出真正的文件
      filename: isEnvProduction
        ? "static/js/[name].[contenthash:8].js"
        : "static/js/bundle.js",
      //如果使用了代码分割的话,这里有额外的JS代码块文件
      chunkFilename: isEnvProduction
        ? "static/js/[name].[contenthash:8].chunk.js"
        : "static/js/[name].chunk.js",
      //打后后的文件的访问路径
      publicPath: paths.publicUrlOrPath,
    },
    optimization: {
      minimize: isEnvProduction,
      minimizer: [
        //压缩JS
        new TerserPlugin({}),
        //压缩CSS
        new OptimizeCSSAssetsPlugin({}),
      ],
      //自动分割第三方模块和公共模块
      splitChunks: {
        chunks: "all",
        name: false,
      },
      //为了长期缓存保持运行时代码块是单独的文件
      runtimeChunk: {
        name: (entrypoint) => `runtime-${entrypoint.name}`,
      },
    },
    resolve: {
      //设置modules的目录
      modules: ["node_modules", paths.appNodeModules],
      //指定扩展名
      extensions: paths.moduleFileExtensions.map((ext) => `.${ext}`),
      alias: {
        //设置别名
        "react-native": "react-native-web",
      },
      plugins: [
        PnpWebpackPlugin,
        //防止用户引用在src或者node_modules之外的文件
        new ModuleScopePlugin(paths.appSrc, [paths.appPackageJson]),
      ],
    },
    resolveLoader: {
      plugins: [PnpWebpackPlugin.moduleLoader(module)],
    },
    module: {
      rules: [
        //在babel处理之前执行linter
        {
          test: /\.(js|mjs|jsx|ts|tsx)$/,
          enforce: "pre",
          use: [
            {
              loader: require.resolve("eslint-loader"),
            },
          ],
          include: paths.appSrc,
        },
        {
          //OneOf会遍历接下来的loader直到找一个匹配要求的,如果没有匹配的会走file-loader
          oneOf: [
            {
              test: [/\.bmp$/, /\.gif$/, /\.jpe?g$/, /\.png$/],
              loader: require.resolve("url-loader"),
            },
            {
              test: /\.(js|mjs|jsx|ts|tsx)$/,
              include: paths.appSrc,
              loader: require.resolve("babel-loader"),
            },
            {
              test: /\.(js|mjs)$/,
              loader: require.resolve("babel-loader"),
            },
            {
              test: cssRegex,
              //用于配置css-loader,作用于@import资源之前有多少个loader
              //0=>无(默认) 1=>postcss-loader 2 postcss-loader sass-loader
              use: getStyleLoaders({ importLoaders: 1 }),
            },
            {
              test: sassRegex,
              //postcss-loader  sass-loader
              use: getStyleLoaders({ importLoaders: 3 }, "sass-loader"),
            },
            {
              loader: require.resolve("file-loader"),
              exclude: [/\.(js|mjs|jsx|ts|tsx)$/, /\.html$/, /\.json$/],
              options: {
                name: "static/media/[name].[hash:8].[ext]",
              },
            },
          ],
        },
      ],
    },
    plugins: [
      //使用插入的script标签生成一个index.html标签
      new HtmlWebpackPlugin({
        inject: true,
        template: paths.appHtml,
      }),
      isEnvProduction &&
        shouldInlineRuntimeChunk &&
        new InlineChunkHtmlPlugin(HtmlWebpackPlugin, [/runtime-.+[.]js/]),
      //保证在index.html中获取到环境变量public URL可以通过%PUBLIC_URL%获取
      new InterpolateHtmlPlugin(HtmlWebpackPlugin, env.raw),
      //模块找不到的时候提供一些必要上下文信息
      new ModuleNotFoundPlugin(paths.appPath),
      //保证在JS中获取到环境变量if (process.env.NODE_ENV === 'production') { ... }
      new webpack.DefinePlugin(env.stringified),
      //模块热更新插件
      isEnvDevelopment && new webpack.HotModuleReplacementPlugin(),
      //当你大小写拼错的时候进行提示
      isEnvDevelopment && new CaseSensitivePathsPlugin(),
      //重新安装模块后不用重新启动开发服务器
      isEnvDevelopment &&
        new WatchMissingNodeModulesPlugin(paths.appNodeModules),
      //提取CSS
      isEnvProduction &&
        new MiniCssExtractPlugin({
          filename: "static/css/[name].[contenthash:8].css",
          chunkFilename: "static/css/[name].[contenthash:8].chunk.css",
        }),
      //生成一个manifest文件
      new ManifestPlugin({
        fileName: "asset-manifest.json",
        publicPath: paths.publicUrlOrPath,
        generate: (seed, files, entrypoints) => {
          const manifestFiles = files.reduce((manifest, file) => {
            manifest[file.name] = file.path;
            return manifest;
          }, seed);
          const entrypointFiles = entrypoints.main.filter(
            (fileName) => !fileName.endsWith(".map")
          );

          return {
            files: manifestFiles,
            entrypoints: entrypointFiles,
          };
        },
      }),
    ].filter(Boolean),
  };
};

5.3.2 paths.js #

paths.js

'use strict';

const path = require('path');
const fs = require('fs');

//当前的工作目录
const appDirectory = fs.realpathSync(process.cwd());
//从相对路径中解析绝对路径
const resolveApp = relativePath => path.resolve(appDirectory, relativePath);
//获取PublicUrlOrPath
const publicUrlOrPath = require(resolveApp("package.json")).homepage || process.env.PUBLIC_URL || "";
//默认的模块扩展名
const moduleFileExtensions = [
  'web.mjs',
  'mjs',
  'web.js',
  'js',
  'web.ts',
  'ts',
  'web.tsx',
  'tsx',
  'json',
  'web.jsx',
  'jsx',
];
//解析模块路径
const resolveModule = (resolveFn, filePath) => {
  const extension = moduleFileExtensions.find(extension =>
    fs.existsSync(resolveFn(`${filePath}.${extension}`))
  );

  if (extension) {
    return resolveFn(`${filePath}.${extension}`);
  }

  return resolveFn(`${filePath}.js`);
};

module.exports = {
  dotenv: resolveApp('.env'),//客户端环境变量的文件名路径
  appPath: resolveApp('.'),//当前工作路径
  appBuild: resolveApp('build'),//输出的build目标路径
  appPublic: resolveApp('public'),//public目录
  appHtml: resolveApp('public/index.html'),//html文件绝对路径
  appIndexJs: resolveModule(resolveApp, 'src/index'),//入口文件
  appPackageJson: resolveApp('package.json'),//package.json文件路径
  appSrc: resolveApp('src'),//src路径
  appTsConfig: resolveApp('tsconfig.json'),
  appJsConfig: resolveApp('jsconfig.json'),
  appNodeModules: resolveApp('node_modules'),
  publicUrlOrPath,
};

module.exports.moduleFileExtensions = moduleFileExtensions;

5.3.3 env.js #

env.js

'use strict';

const fs = require('fs');
const path = require('path');
const paths = require('./paths');
//一般可能是production或者development set NODE_ENV=development
const NODE_ENV = process.env.NODE_ENV;

//环境变量的文件路径
const dotenvFiles = [
  `${paths.dotenv}.${NODE_ENV}.local`, // .env.development.local
  `${paths.dotenv}.${NODE_ENV}`,       // .env.development
  //在测试环境下不要包括.env.local
  NODE_ENV !== 'test' && `${paths.dotenv}.local`, // .env.local
  paths.dotenv,//.env
].filter(Boolean);

//从.env*文件中加载环境变量
dotenvFiles.forEach(dotenvFile => {
  if (fs.existsSync(dotenvFile)) {
    require('dotenv-expand')(
      require('dotenv').config({
        path: dotenvFile,
      })
    );
  }
});

//支持通过NODE_PATH加载解析模块 set NODE_PATH=modules;extraModules
const appDirectory = fs.realpathSync(process.cwd());
process.env.NODE_PATH = (process.env.NODE_PATH || '')
  .split(path.delimiter)
  .filter(folder => folder && !path.isAbsolute(folder))
  .map(folder => path.resolve(appDirectory, folder))
  .join(path.delimiter);

//获取NODE_ENV and REACT_APP_*环境变量,并且准备通过DefinePlugin插入应用
//set REACT_APP_NAME=zhufeng
const REACT_APP = /^REACT_APP_/i;
function getClientEnvironment(publicUrl) {
  const raw = Object.keys(process.env)
    .filter((key) => REACT_APP.test(key))
    .reduce(
      (env, key) => {
        env[key] = process.env[key];
        return env;
      },
      {
        //决定当前是否处于开发模式
        NODE_ENV: process.env.NODE_ENV || "development",
        //用来解析处于public下面的正确资源路径
        PUBLIC_URL: publicUrl,
      }
    );
  //把所有的值转成字符串以便在DefinePlugin中使用
  const stringified = {
    "process.env": Object.keys(raw).reduce((env, key) => {
      env[key] = JSON.stringify(raw[key]);
      return env;
    }, {}),
  };

  return { raw, stringified };
}

module.exports = getClientEnvironment;

5.3.4 webpackDevServer.config.js #

'use strict';

const fs = require('fs');
const errorOverlayMiddleware = require('react-dev-utils/errorOverlayMiddleware');
const evalSourceMapMiddleware = require('react-dev-utils/evalSourceMapMiddleware');
const ignoredFiles = require('react-dev-utils/ignoredFiles');
const redirectServedPath = require('react-dev-utils/redirectServedPathMiddleware');
const paths = require('./paths');
const host = process.env.HOST || '0.0.0.0';

module.exports = function(proxy, allowedHost) {
  return {
    //禁用主机检查
    disableHostCheck: true,
    //启动gzip压缩
    compress: true,
    //禁用WebpackDevServer自己的日志,警告和错误还是可以显示的
    clientLogLevel: "none",
    //静态文件根目录
    contentBase: paths.appPublic,
    contentBasePublicPath: paths.publicUrlOrPath,
    //默认情况下contentBase里的文件变更不会触发页面刷新
    watchContentBase: true,
    //启用热更新
    hot: true,
    //使用ws而非socketjs-node模块
    transportMode: "ws",
    //不需要注入WS客户端
    injectClient: false,
    //访问路径
    publicPath: paths.publicUrlOrPath.slice(0, -1),
    //更少的WebpackDevServer日志
    quiet: true,
    watchOptions: {
      ignored: ignoredFiles(paths.appSrc), //不要监控src目录
    },
    host,
    historyApiFallback: {
      //禁用dotRule
      disableDotRule: true,
      index: paths.publicUrlOrPath,
    },
    public: allowedHost,
    //proxy会在before和after之间执行
    proxy,
    before(app, server) {
      //在出错的时候获取源码内容
      app.use(evalSourceMapMiddleware(server));
      //让我们从运行时错误打开文件
      app.use(errorOverlayMiddleware());
      //由于代理注册的中间件 
      if (fs.existsSync(paths.proxySetup)) {
        require(paths.proxySetup)(app);
      }
    },
    after(app) {
      //如果URL不匹配重定向到`PUBLIC_URL` or `homepage` from `package.json`
      app.use(redirectServedPath(paths.publicUrlOrPath));
    },
  };
};

5.3.5 webpack.dev.config.js #

webpack.dev.config.js


const { merge } = require("webpack-merge");
let config = require('./webpack.config');
let devServerConfig = require('./webpackDevServer.config');
module.exports = merge(config('development'), {
  devServer: devServerConfig()
});

5.3.6 postcss.config.js #

postcss.config.js

module.exports = {
  plugins: [
    require("autoprefixer")({ overrideBrowserslist: ["> 0.15% in CN"] }), // 自动添加css前缀
  ],
};

5.3.7 .eslintrc.json #

{
    "env": {
        "browser": true,
        "es2020": true
    },
    "parserOptions": {
        "ecmaVersion": 2020,
        "sourceType": "module"
    },
    "rules": {
    }
}

5.3.8 package.json #

{
    "scripts": {
      "build": "webpack --env=production",
      "start": "webpack-dev-server --env=development --config webpack.dev.config.js"
    }
}

6. source map是什么?生产环境怎么用? #

6.1 source map的类型 #

类型 含义
source-map 原始代码 最好的sourcemap质量有完整的结果,但是会很慢
eval-source-map 原始代码 同样道理,但是最高的质量和最低的性能
cheap-module-eval-source-map 原始代码(只有行内) 同样道理,但是更高的质量和更低的性能
cheap-eval-source-map 转换代码(行内) 每个模块被eval执行,并且sourcemap作为eval的一个dataurl
eval 生成代码 每个模块都被eval执行,并且存在@sourceURL,带eval的构建模式能cache SourceMap
cheap-source-map 转换代码(行内) 生成的sourcemap没有列映射,从loaders生成的sourcemap没有被使用
cheap-module-source-map 原始代码(只有行内) 与上面一样除了每行特点的从loader中进行映射

看似配置项很多, 其实只是五个关键字eval、source-map、cheap、module和inline的任意组合

关键字 含义
eval 使用eval包裹模块代码
source-map 产生.map文件
cheap 不包含列信息(关于列信息的解释下面会有详细介绍)也不包含loader的sourcemap
module 包含loader的sourcemap(比如jsx to js ,babel的sourcemap),否则无法定义源文件
inline 将.map作为DataURI嵌入,不单独生成.map文件

6.2 如何选择source map的类型 #

7.如何利用webpack来优化前端性能? #

7.1. 安装 #

cnpm i react react-dom  -S
cnpm install  webpack webpack-cli webpack-dev-server image-webpack-loader mini-css-extract-plugin purgecss-webpack-plugin babel-loader @babel/core @babel/preset-env @babel/preset-react terser-webpack-plugin html-webpack-plugin optimize-css-assets-webpack-plugin mini-css-extract-plugin qiniu -D

7.2.压缩JS #

  optimization: {
    minimize: true,
    minimizer: [
      //压缩JS
+     new TerserPlugin({})
    ]
  },

7.3. 压缩CSS #

  optimization: {
    minimize: true,
    minimizer: [
      //压缩CSS
+      new OptimizeCSSAssetsPlugin({}),
    ]
  },

7.4. 压缩图片 #

      {
        test: /\.(png|svg|jpg|gif|jpeg|ico)$/,
        use: [
          "file-loader",
          {
+            loader: "image-webpack-loader",
+            options: {
+              mozjpeg: {
+                progressive: true,
+                quality: 65,
+              },
+              optipng: {
+                enabled: false,
+              },
+              pngquant: {
+                quality: "65-90",
+                speed: 4,
+              },
+              gifsicle: {
+                interlaced: false,
+              },
+              webp: {
+                quality: 75,
+              }
+            }
+          }
        ]
      }

7.5. 清除无用的CSS #

const path = require("path");
+const MiniCssExtractPlugin = require("mini-css-extract-plugin");
+const PurgecssPlugin = require("purgecss-webpack-plugin");
module.exports = {
  module: {
    rules: [
       {
        test: /\.css$/,
        include: path.resolve(__dirname, "src"),
        exclude: /node_modules/,
        use: [
          {
+            loader: MiniCssExtractPlugin.loader,
          },
          "css-loader",
        ],
      }
    ]
  },
  plugins: [
+    new MiniCssExtractPlugin({
+      filename: "[name].css",
+    }),
+    new PurgecssPlugin({
+      paths: glob.sync(`${PATHS.src}/**/*`,  { nodir: true }),
+    })
  ]
  devServer: {},
};

7.6. Tree Shaking #

module.exports = {
+    mode:'production',
+    devtool:false,
     module: {
        rules: [
            {
                test: /\.js/,
                include: path.resolve(__dirname, "src"),
                use: [
                    {
                        loader: "babel-loader",
                        options: {
+                            presets: [["@babel/preset-env", { "modules": false }]],
                        },
                    },
                ],
            }
     }
}

7.7. Scope Hoisting #

hello.js

export default 'Hello';

index.js

import str from './hello.js';
console.log(str);

main.js

var hello = ('hello');
console.log(hello);

7.8. 代码分割 #

7.8.1 入口点分割 #

entry: {
        index: "./src/index.js",
        login: "./src/login.js"
}

7.8.2 动态导入和懒加载 #

7.8.2.1 hello.js #

hello.js

module.exports = "hello";

index.js

document.querySelector('#clickBtn').addEventListener('click',() => {
    import('./hello').then(result => {
        console.log(result.default);
    });
});

index.html

<button id="clickBtn">点我</button>
7.8.2.2 按需加载 #
7.8.2.2.1 index.js #

index.js

import React, { Component, Suspense } from "react";
import ReactDOM from "react-dom";
import Loading from "./components/Loading";
/* function lazy(loadFunction) {
  return class LazyComponent extends React.Component {
    state = { Comp: null };
    componentDidMount() {
      loadFunction().then((result) => {
        this.setState({ Comp: result.default });
      });
    }
    render() {
      let Comp = this.state.Comp;
      return Comp ? <Comp {...this.props} /> : null;
    }
  };
} */
const AppTitle = React.lazy(() =>
  import(/* webpackChunkName: "title" */ "./components/Title")
);

class App extends Component {
  constructor(){
    super();
    this.state = {visible:false};
  }
  show(){
    this.setState({ visible: true });
  };
  render() {
    return (
      <>
        {this.state.visible && (
          <Suspense fallback={<Loading />}>
            <AppTitle />
          </Suspense>
        )}
        <button onClick={this.show.bind(this)}>加载</button>
      </>
    );
  }
}
ReactDOM.render(<App />, document.querySelector("#root"));

7.8.2.2.2 Loading.js #

src\components\Loading.js

import React, { Component, Suspense } from "react";
export default (props) => {
  return <p>Loading</p>;
};
7.8.2.2.3 Title.js #

src\components\Title.js

import React, { Component, Suspense } from "react";
export default props=>{
  return <p>Title</p>;
}

7.8.3 preload(预先加载) #

prefetchpreload

<link rel="preload" as="script" href="utils.js">
import(
  `./utils.js`
  /* webpackPreload: true */
  /* webpackChunkName: "utils" */
)

7.8.4 prefetch(预先拉取) #

<link rel="prefetch" href="utils.js" as="script">
button.addEventListener('click', () => {
  import(
    `./utils.js`
    /* webpackPrefetch: true */
    /* webpackChunkName: "utils" */
  ).then(result => {
    result.default.log('hello');
  })
});

7.8.5 preload vs prefetch #

7.8.6 提取公共代码 #

7.8.6.2 如何提取 #
7.8.6.3 splitChunks #
7.8.6.3.1 module chunk bundle #
7.8.6.3.2 默认配置 #

webpack.config.js

  entry: {
    page1: "./src/page1.js",
    page2: "./src/page2.js",
    page3: "./src/page3.js",
  },
 optimization: {
  splitChunks: {
      chunks: "all", //默认作用于异步chunk,值为all/initial/async
      minSize: 0, //默认值是30kb,代码块的最小尺寸
      minChunks: 1, //被多少模块共享,在分割之前模块的被引用次数
      maxAsyncRequests: 2, //限制异步模块内部的并行最大请求数的,说白了你可以理解为是每个import()它里面的最大并行请求数量
      maxInitialRequests: 4, //限制入口的拆分数量
      name: true, //打包后的名称,默认是chunk的名字通过分隔符(默认是~)分隔开,如vendor~
      automaticNameDelimiter: "~", //默认webpack将会使用入口名和代码块的名称生成命名,比如 'vendors~main.js'
      cacheGroups: {
        //设置缓存组用来抽取满足不同规则的chunk,下面以生成common为例
        vendors: {
          chunks: "all",
          test: /node_modules/, //条件
          priority: -10, ///优先级,一个chunk很可能满足多个缓存组,会被抽取到优先级高的缓存组中,为了能够让自定义缓存组有更高的优先级(默认0),默认缓存组的priority属性为负值.
        },
        commons: {
          chunks: "all",
          minSize: 0, //最小提取字节数
          minChunks: 2, //最少被几个chunk引用
          priority: -20
        }
      }
    }

src\page1.js

import utils1 from "./module1";
import utils2 from "./module2";
import $ from "jquery";
console.log(utils1, utils2, $);
import(/* webpackChunkName: "asyncModule1" */ "./asyncModule1");

src\page2.js

import utils1 from "./module1";
import utils2 from "./module2";
import $ from "jquery";
console.log(utils1, utils2, $);

src\page3.js

import utils1 from "./module1";
import utils3 from "./module3";
import $ from "jquery";
console.log(utils1, utils3, $);

src\module1.js

console.log("module1");

src\module2.js

console.log("module2");

src\module3.js

console.log("module3");

src\asyncModule1.js

import _ from 'lodash';
console.log(_);
                             Asset       Size                     Chunks             Chunk Names
             asyncModule1.chunk.js  740 bytes               asyncModule1  [emitted]  asyncModule1
                        index.html  498 bytes                             [emitted]
                          page1.js   10.6 KiB                      page1  [emitted]  page1
              page1~page2.chunk.js  302 bytes                page1~page2  [emitted]  page1~page2
        page1~page2~page3.chunk.js  308 bytes          page1~page2~page3  [emitted]  page1~page2~page3
                          page2.js   7.52 KiB                      page2  [emitted]  page2
                          page3.js   7.72 KiB                      page3  [emitted]  page3
     vendors~asyncModule1.chunk.js    532 KiB       vendors~asyncModule1  [emitted]  vendors~asyncModule1
vendors~page1~page2~page3.chunk.js    282 KiB  vendors~page1~page2~page3  [emitted]  vendors~page1~page2~page3
Entrypoint page1 = vendors~page1~page2~page3.chunk.js page1~page2~page3.chunk.js page1~page2.chunk.js page1.js
Entrypoint page2 = vendors~page1~page2~page3.chunk.js page1~page2~page3.chunk.js page1~page2.chunk.js page2.js
Entrypoint page3 = vendors~page1~page2~page3.chunk.js page1~page2~page3.chunk.js page3.js

splitChunks

7.9 CDN #

7.9.1 webpack.config.js #

const path = require("path");
const MiniCssExtractPlugin = require("mini-css-extract-plugin");
const PurgecssPlugin = require("purgecss-webpack-plugin");
const TerserPlugin = require("terser-webpack-plugin");
const OptimizeCSSAssetsPlugin = require("optimize-css-assets-webpack-plugin");
const HtmlWebpackPlugin = require("html-webpack-plugin");
const UploadPlugin = require("./plugins/UploadPlugin");
const glob = require("glob");
const PATHS = {
    src: path.join(__dirname, "src"),
};
module.exports = {
  mode: "development",
  devtool: false,
  context: process.cwd(),
  entry: {
    main: "./src/index.js",
  },
  output: {
    path: path.resolve(__dirname, "dist"),
+    filename: "[name].[hash].js",
+    chunkFilename: "[name].[hash].chunk.js",
+    publicPath: "http://img.zhufengpeixun.cn/",
  },
  optimization: {
    minimize: true,
    minimizer: [
      //压缩JS
      /* new TerserPlugin({
        sourceMap: false,
        extractComments: false,
      }),
      //压缩CSS
      new OptimizeCSSAssetsPlugin({}), */
    ],
    //自动分割第三方模块和公共模块
    splitChunks: {
      chunks: "all", //默认作用于异步chunk,值为all/initial/async
      minSize: 0, //默认值是30kb,代码块的最小尺寸
      minChunks: 1, //被多少模块共享,在分割之前模块的被引用次数
      maxAsyncRequests: 2, //限制异步模块内部的并行最大请求数的,说白了你可以理解为是每个import()它里面的最大并行请求数量
      maxInitialRequests: 4, //限制入口的拆分数量
      name: true, //打包后的名称,默认是chunk的名字通过分隔符(默认是~)分隔开,如vendor~
      automaticNameDelimiter: "~", //默认webpack将会使用入口名和代码块的名称生成命名,比如 'vendors~main.js'
      cacheGroups: {
        //设置缓存组用来抽取满足不同规则的chunk,下面以生成common为例
        vendors: {
          chunks: "all",
          test: /node_modules/, //条件
          priority: -10, ///优先级,一个chunk很可能满足多个缓存组,会被抽取到优先级高的缓存组中,为了能够让自定义缓存组有更高的优先级(默认0),默认缓存组的priority属性为负值.
        },
        commons: {
          chunks: "all",
          minSize: 0, //最小提取字节数
          minChunks: 2, //最少被几个chunk引用
          priority: -20,
          reuseExistingChunk: true, //如果该chunk中引用了已经被抽取的chunk,直接引用该chunk,不会重复打包代码
        },
      },
    },
    //为了长期缓存保持运行时代码块是单独的文件
    /*  runtimeChunk: {
      name: (entrypoint) => `runtime-${entrypoint.name}`,
    }, */
  },
  module: {
    rules: [
      {
        test: /\.js/,
        include: path.resolve(__dirname, "src"),
        use: [
          {
            loader: "babel-loader",
            options: {
              presets: [
                ["@babel/preset-env", { modules: false }],
                "@babel/preset-react",
              ],
            },
          },
        ],
      },
      {
        test: /\.css$/,
        include: path.resolve(__dirname, "src"),
        exclude: /node_modules/,
        use: [
          {
            loader: MiniCssExtractPlugin.loader,
          },
          "css-loader",
        ],
      },
      {
        test: /\.(png|svg|jpg|gif|jpeg|ico)$/,
        use: [
          "file-loader",
          {
            loader: "image-webpack-loader",
            options: {
              mozjpeg: {
                progressive: true,
                quality: 65,
              },
              optipng: {
                enabled: false,
              },
              pngquant: {
                quality: "65-90",
                speed: 4,
              },
              gifsicle: {
                interlaced: false,
              },
              webp: {
                quality: 75,
              },
            },
          },
        ],
      },
    ],
  },
  plugins: [
    new HtmlWebpackPlugin({
      inject: true,
      template: "./src/index.html",
    }),
    new MiniCssExtractPlugin({
+      filename: "[name].[hash].css",
    }),
    new PurgecssPlugin({
      paths: glob.sync(`${PATHS.src}/**/*`, { nodir: true }),
    }),
    new UploadPlugin({}),
  ],
  devServer: {},
};

7.9.2 UploadPlugin.js #

const qiniu = require("qiniu");
const path = require("path");
//https://developer.qiniu.com/kodo/sdk/1289/nodejs
require("dotenv").config();
const defaultAccessKey = process.env.accessKey;
const defaultSecretKey = process.env.secretKey;
class UploadPlugin {
  constructor(options) {
    this.options = options || {};
  }
  apply(compiler) {
    compiler.hooks.afterEmit.tap("UploadPlugin", (compilation) => {
      let assets = compilation.assets;
      let promises = Object.keys(assets).filter(item=>!item.includes('.html')).map(this.upload.bind(this));
      Promise.all(promises).then((err, data) => console.log(err, data));
    });
  }
  upload(filename) {
    return new Promise((resolve, reject) => {
      let {
        bucket = "cnpmjs",
        accessKey = defaultAccessKey,
        secretKey = defaultSecretKey,
      } = this.options;
      let mac = new qiniu.auth.digest.Mac(accessKey, secretKey);
      let options = {
        scope: bucket,
      };

      let putPolicy = new qiniu.rs.PutPolicy(options);
      let uploadToken = putPolicy.uploadToken(mac);
      let config = new qiniu.conf.Config();

      let localFile = path.resolve(__dirname, "../dist", filename);
      let formUploader = new qiniu.form_up.FormUploader(config);
      let putExtra = new qiniu.form_up.PutExtra();
      formUploader.putFile(
        uploadToken,
        filename,
        localFile,
        putExtra,
        (err, body, info) => {
          err ? reject(err) : resolve(body);
        }
      );
    });
  }
}

module.exports = UploadPlugin;

8. webpack中hash、chunkhash、contenthash区别? #

指纹占位符

占位符名称 含义
ext 资源后缀名
name 文件名称
path 文件的相对路径
folder 文件所在的文件夹
hash 每次webpack构建时生成一个唯一的hash值
chunkhash 根据chunk生成hash值,来源于同一个chunk,则hash值就一样
contenthash 根据内容生成hash值,文件内容相同hash值就相同

8.1 hash #

const path = require("path");
const glob = require("glob");
const PurgecssPlugin = require("purgecss-webpack-plugin");
const MiniCssExtractPlugin = require('mini-css-extract-plugin');
const PATHS = {
  src: path.join(__dirname, 'src')
}
module.exports = {
  mode: "production",
+  entry: {
+    main: './src/index.js',
+    vender:['lodash']
+  },
  output:{
    path:path.resolve(__dirname,'dist'),
+    filename:'[name].[hash].js'
  },
  devServer:{
    hot:false
  },
  module: {
    rules: [
      {
        test: /\.js/,
        include: path.resolve(__dirname, "src"),
        use: [
          {
            loader:'thread-loader',
            options:{
              workers:3
            }
          },
          {
            loader: "babel-loader",
            options: {
              presets: ["@babel/preset-env", "@babel/preset-react"],
            },
          },
        ],
      },
      {
        test: /\.css$/,
        include: path.resolve(__dirname, "src"),
        exclude: /node_modules/,
        use: [
          {
            loader: MiniCssExtractPlugin.loader,
          },
          "css-loader",
        ],
      },
    ],
  },
  plugins: [
    new MiniCssExtractPlugin({
+      filename: "[name].[hash].css"
    }),
    new PurgecssPlugin({
      paths: glob.sync(`${PATHS.src}/**/*`,  { nodir: true }),
    }),
  ],
};

8.2 chunkhash #

const path = require("path");
const glob = require("glob");
const PurgecssPlugin = require("purgecss-webpack-plugin");
const MiniCssExtractPlugin = require('mini-css-extract-plugin');
const PATHS = {
  src: path.join(__dirname, 'src')
}
module.exports = {
  mode: "production",
  entry: {
    main: './src/index.js',
    vender:['lodash']
  },
  output:{
    path:path.resolve(__dirname,'dist'),
+    filename:'[name].[chunkhash].js'
  },
  devServer:{
    hot:false
  },
  module: {
    rules: [
      {
        test: /\.js/,
        include: path.resolve(__dirname, "src"),
        use: [
          {
            loader:'thread-loader',
            options:{
              workers:3
            }
          },
          {
            loader: "babel-loader",
            options: {
              presets: ["@babel/preset-env", "@babel/preset-react"],
            },
          },
        ],
      },
      {
        test: /\.css$/,
        include: path.resolve(__dirname, "src"),
        exclude: /node_modules/,
        use: [
          {
            loader: MiniCssExtractPlugin.loader,
          },
          "css-loader",
        ],
      },
    ],
  },
  plugins: [
    new MiniCssExtractPlugin({
+      filename: "[name].[chunkhash].css"
    }),
    new PurgecssPlugin({
      paths: glob.sync(`${PATHS.src}/**/*`,  { nodir: true }),
    }),
  ],
};

8.3 contenthash #

const path = require("path");
const glob = require("glob");
const PurgecssPlugin = require("purgecss-webpack-plugin");
const MiniCssExtractPlugin = require('mini-css-extract-plugin');
const PATHS = {
  src: path.join(__dirname, 'src')
}
module.exports = {
  mode: "production",
  entry: {
    main: './src/index.js',
    vender:['lodash']
  },
  output:{
    path:path.resolve(__dirname,'dist'),
    filename:'[name].[chunkhash].js'
  },
  devServer:{
    hot:false
  },
  module: {
    rules: [
      {
        test: /\.js/,
        include: path.resolve(__dirname, "src"),
        use: [
          {
            loader:'thread-loader',
            options:{
              workers:3
            }
          },
          {
            loader: "babel-loader",
            options: {
              presets: ["@babel/preset-env", "@babel/preset-react"],
            },
          },
        ],
      },
      {
        test: /\.css$/,
        include: path.resolve(__dirname, "src"),
        exclude: /node_modules/,
        use: [
          {
            loader: MiniCssExtractPlugin.loader,
          },
          "css-loader",
        ],
      },
    ],
  },
  plugins: [
    new MiniCssExtractPlugin({
+      filename: "[name].[contenthash].css"
    }),
    new PurgecssPlugin({
      paths: glob.sync(`${PATHS.src}/**/*`,  { nodir: true }),
    }),
  ],
};

9.如何对bundle体积进行监控和分析? #

9.1 安装 #

cnpm i webpack-bundle-analyzer -D
const {BundleAnalyzerPlugin} = require('webpack-bundle-analyzer')
module.exports={
  plugins: [
    new BundleAnalyzerPlugin()  // 使用默认配置
    // 默认配置的具体配置项
    // new BundleAnalyzerPlugin({
    //   analyzerMode: 'server',
    //   analyzerHost: '127.0.0.1',
    //   analyzerPort: '8888',
    //   reportFilename: 'report.html',
    //   defaultSizes: 'parsed',
    //   openAnalyzer: true,
    //   generateStatsFile: false,
    //   statsFilename: 'stats.json',
    //   statsOptions: null,
    //   excludeAssets: null,
    //   logLevel: info
    // })
  ]
}
{
 "scripts": {
    "dev": "webpack --config webpack.dev.js --progress"
  }
}

9.2 先生成文件再分析 #

webpack.config.js

const {BundleAnalyzerPlugin} = require('webpack-bundle-analyzer')
module.exports={
  plugins: [
    new BundleAnalyzerPlugin({
      analyzerMode: 'disabled', // 不启动展示打包报告的http服务器
      generateStatsFile: true, // 是否生成stats.json文件
    }),
  ]
}
{
 "scripts": {
    "generateAnalyzFile": "webpack --profile --json > stats.json", // 生成分析文件
    "analyz": "webpack-bundle-analyzer --port 8888 ./dist/stats.json" // 启动展示打包报告的http服务器
  }
}
npm run generateAnalyzFile
npm run analyz

10.如何提高webpack的构建速度? #

10.1 费时分析 #

const SpeedMeasureWebpackPlugin = require('speed-measure-webpack-plugin');
const smw = new SpeedMeasureWebpackPlugin();
module.exports =smw.wrap({
});

10.2 缩小范围 #

10.2.1 extensions #

指定extension之后可以不用在require或是import的时候加文件扩展名,会依次尝试添加扩展名进行匹配

resolve: {
  extensions: [".js",".jsx",".json",".css"]
},

10.2.2 alias #

配置别名可以加快webpack查找模块的速度

const bootstrap = path.resolve(__dirname,'node_modules/_bootstrap@3.3.7@bootstrap/dist/css/bootstrap.css');
resolve: {
+    alias:{
+        "bootstrap":bootstrap
+    }
},

10.2.3 modules #

10.2.4 mainFields #

默认情况下package.json 文件则按照文件中 main 字段的文件名来查找文件

resolve: {
  // 配置 target === "web" 或者 target === "webworker" 时 mainFields 默认值是:
  mainFields: ['browser', 'module', 'main'],
  // target 的值为其他时,mainFields 默认值为:
  mainFields: ["module", "main"],
}

10.2.5 mainFiles #

当目录下没有 package.json 文件时,我们说会默认使用目录下的 index.js 这个文件,其实这个也是可以配置的

resolve: {
  mainFiles: ['index'], // 你可以添加其他默认使用的文件名
},

10.2.6 resolveLoader #

resolve.resolveLoader用于配置解析 loader 时的 resolve 配置,默认的配置:

module.exports = {
  resolveLoader: {
    modules: [ 'node_modules' ],
    extensions: [ '.js', '.json' ],
    mainFields: [ 'loader', 'main' ]
  }
};

10.3 noParse #

10.4 IgnorePlugin #

IgnorePlugin用于忽略某些特定的模块,让 webpack 不把这些指定的模块打包进去

import moment from  'moment';
console.log(moment);
new webpack.IgnorePlugin(/^\.\/locale/,/moment$/)

10.5 日志优化 #

预设 替代 描述
errors-only none 只在错误时输出
minimal none 发生错误和新的编译时输出
none false 没有输出
normal true 标准输出
verbose none 全部输出

10.5.1 friendly-errors-webpack-plugin #

cnpm i friendly-errors-webpack-plugin
+ stats:'verbose',
  plugins:[
+   new FriendlyErrorsWebpackPlugin()
  ]

编译完成后可以通过echo $?获取错误码,0为成功,非0为失败

10.6.DLL #

10.6.1 定义Dll #

webpack.dll.config.js

const path = require("path");

const DllPlugin = require("webpack/lib/DllPlugin");
module.exports = {
  mode: "development",
  entry: {
    react: ["react", "react-dom"],
  },
  output: {
    path: path.resolve(__dirname, "dist"),
    filename: "[name].dll.js", //react.dll.js
    library: "_dll_[name]",
  },
  plugins: [
    new DllPlugin({
      name: "_dll_[name]",
      path: path.join(__dirname, "dist", "[name].manifest.json"), //react.manifest.json
    }),
  ],
};

webpack --config webpack.dll.config.js --mode=development

10.6.2 使用动态链接库文件 #

const path = require("path");
const glob = require("glob");
const PurgecssPlugin = require("purgecss-webpack-plugin");
const MiniCssExtractPlugin = require('mini-css-extract-plugin');
+const DllReferencePlugin = require("webpack/lib/DllReferencePlugin.js");
const PATHS = {
  src: path.join(__dirname, 'src')
}
module.exports = {
  mode: "development",
  entry: "./src/index.js",
  module: {
    rules: [
      {
        test: /\.js/,
        include: path.resolve(__dirname, "src"),
        use: [
          {
            loader: "babel-loader",
            options: {
              presets: ["@babel/preset-env", "@babel/preset-react"],
            },
          },
        ],
      },
      {
        test: /\.css$/,
        include: path.resolve(__dirname, "src"),
        exclude: /node_modules/,
        use: [
          {
            loader: MiniCssExtractPlugin.loader,
          },
          "css-loader",
        ],
      },
    ],
  },
  plugins: [
    new MiniCssExtractPlugin({
      filename: "[name].css",
    }),
    new PurgecssPlugin({
      paths: glob.sync(`${PATHS.src}/**/*`,  { nodir: true }),
    }),
+    new DllReferencePlugin({
+      manifest: require("./dist/react.manifest.json"),
+    }),
  ],
};

webpack --config webpack.config.js --mode development

10.6.3 html中使用 #

<script src="react.dll.js"></script>
<script src="bundle.js"></script>

10.7 利用缓存 #

10.7.1 babel-loader #

 {
    test: /\.js$/,
    exclude: /node_modules/,
    use: [{
      loader: "babel-loader",
      options: {
        cacheDirectory: true
      }
    }]
  },

10.7.2 cache-loader #

cnpm i  cache-loader -D
const loaders = ['babel-loader'];
module.exports = {
  module: {
    rules: [
      {
        test: /\.js$/,
        use: [
          'cache-loader',
          ...loaders
        ],
        include: path.resolve('src')
      }
    ]
  }
}

10.7.3 hard-source-webpack-plugin #

cnpm i  hard-source-webpack-plugin -D 
var HardSourceWebpackPlugin = require('hard-source-webpack-plugin');

module.exports = {
  entry: // ...
  output: // ...
  plugins: [
    new HardSourceWebpackPlugin()
  ]
}

10.7.4 oneOf #

module.exports = {
  module: {
    rules: [
      {
        test: /\.js$/,
        exclude: /node_modules/,
        //优先执行
        enforce: 'pre',
        loader: 'eslint-loader',
        options: {
          fix: true
        }
      },
      {
        // 以下 loader 只会匹配一个
        oneOf: [
          ...,
          {},
          {}
        ]
      }
    ]
  }
}

10.8 多进程处理 #

10.8.1 thread-loader #

cnpm  i thread-loader- D
const path = require("path");
const glob = require("glob");
const PurgecssPlugin = require("purgecss-webpack-plugin");
const MiniCssExtractPlugin = require('mini-css-extract-plugin');
const DllReferencePlugin = require("webpack/lib/DllReferencePlugin.js");
const PATHS = {
  src: path.join(__dirname, 'src')
}
module.exports = {
  mode: "development",
  entry: "./src/index.js",
  module: {
    rules: [
      {
        test: /\.js/,
        include: path.resolve(__dirname, "src"),
        use: [
+          {
+            loader:'thread-loader',
+            options:{
+              workers:3
+            }
+          },
          {
            loader: "babel-loader",
            options: {
              presets: ["@babel/preset-env", "@babel/preset-react"],
            },
          },
        ],
      },
      {
        test: /\.css$/,
        include: path.resolve(__dirname, "src"),
        exclude: /node_modules/,
        use: [
          {
            loader: MiniCssExtractPlugin.loader,
          },
          "css-loader",
        ],
      },
    ],
  },
  plugins: [
    new MiniCssExtractPlugin({
      filename: "[name].css",
    }),
    new PurgecssPlugin({
      paths: glob.sync(`${PATHS.src}/**/*`,  { nodir: true }),
    }),
    new DllReferencePlugin({
      manifest: require("./dist/react.manifest.json"),
    }),
  ],
};

10.8.2 parallel #

terser-webpack-plugin 开启 parallel 参数

const TerserPlugin = require('terser-webpack-plugin');
module.exports = {
    optimization: {
        minimizer: [
            new TerserPlugin({
                parallel: true,
            }),
        ],
    },
};